Intramedullary fixation device and methods for bone fixation and stabilization

Abstract

An internal intramedullary fixation device for the stabilization of bone in arthrodesis and fractures of the foot and hand is disclosed. During implantation in the medullary canal of each bone, the device grasps the edges of the canal, stabilizing the bone (internally) during the natural healing process.

I claim: 
     
       1. An intramedullary fixation device used in bone fixation and stabilization, comprising:
 an arrowhead-shaped distal head comprising a distal end having a tip, the distal head having first, second, third, and fourth outwardly facing side surfaces forming a pyramidal shape, the first and third side surfaces being opposed from each other and forming a first angle, and the second and fourth side surfaces being opposed from each other and forming a second angle, the second angle being different than the first angle, each of the first and third side surfaces having a proximal edge configured to engage tissue and inhibit rotational movement and inhibit axial movement of the distal head in a proximal direction, the distal head being sized to fit within an intramedullary canal of a more-distal phalanx portion of one of a finger and a toe;
 an arrowhead-shaped proximal head comprising a proximal end having a tip, the proximal head having fifth, sixth, seventh, and eighth outwardly facing side surfaces, the fifth and seventh side surfaces being opposed from each other and forming a third angle, and the sixth and eighth side surfaces being opposed from each other and forming a fourth angle, the third angle being different than the fourth angle, each of the fifth and seventh side surfaces having a distal edge configured to engage tissue and inhibit rotational movement and inhibit axial movement of the proximal head in a distal direction, the proximal head being sized to fit within an intramedullary canal of a more-proximal phalanx portion of said one of a finger and a toe; and 
 a rigid body extending between and connecting the distal head and the proximal head, the body having a rigidity sufficient to withstand bending loading applied by the phalanges, the rigid body comprising a main portion, a distal neck portion connecting the rigid body to the distal head, and a proximal neck portion connecting the rigid body to the proximal head, the distal and proximal neck portions having a cross-sectional area smaller than a cross-section area of the main portion such that tissue ingrowth may occur behind the distal head around the distal neck portion and behind the proximal head around the proximal neck portion. 
 
 
     
     
       2. The intramedullary fixation device of  claim 1 , wherein the side surfaces are smooth, planar surfaces. 
     
     
       3. The intramedullary fixation device of  claim 1 , wherein the first angle is larger than the second angle and the third angle is larger than the fourth angle. 
     
     
       4. The intramedullary fixation device of  claim 1 , wherein the first angle is larger than the third angle. 
     
     
       5. The intramedullary fixation device of  claim 1 , wherein the second and fourth side surfaces include proximal ends that relatively smoothly transition to the body. 
     
     
       6. The intramedullary fixation device of  claim 1 , wherein the second and fourth surfaces intersect with a surface of the distal neck portion, and wherein the first and third surfaces do not intersect with a surface of the distal neck portion. 
     
     
       7. The intramedullary fixation device of  claim 1 , further comprising chamfered edges between adjacent outwardly facing side surfaces. 
     
     
       8. The intramedullary fixation device of  claim 1 , wherein the body comprises a first portion and a second portion, the first portion being rigidly angled relative to the second portion at a fixed angle. 
     
     
       9. The intramedullary fixation device of  claim 8 , wherein the first portion has a length less than a length of the second portion. 
     
     
       10. The intramedullary fixation device of  claim 8 , wherein the fixed angle is about a 10 degree angle. 
     
     
       11. The intramedullary fixation device of  claim 8 , wherein the body is cylindrical and the first portion and the second portion have the same diameter. 
     
     
       12. A kit for bone fixation and stabilization, comprising:
 an intramedullary fixation device, comprising:
 an arrowhead-shaped distal head comprising a distal end having a tip, the distal head having first, second, third, and fourth outwardly facing side surfaces forming a pyramidal shape, the first and third side surfaces being opposed from each other and forming a first angle, and the second and fourth side surfaces being opposed from each other and forming a second angle, the second angle being different than the first angle, each of the first and third side surfaces having a proximal edge configured to engage tissue and inhibit rotational movement and inhibit axial movement of the distal head in a proximal direction, the distal head being sized to fit within an intramedullary canal of a more-distal phalanx portion of one of a finger and a toe; 
 an arrowhead-shaped proximal head comprising a proximal end having a tip, the proximal head having fifth, sixth, seventh, and eighth outwardly facing side surfaces, the fifth and seventh side surfaces being opposed from each other and forming a third angle, and the sixth and eighth side surfaces being opposed from each other and forming a fourth angle, the third angle being different than the fourth angle, each of the fifth and seventh side surfaces having a distal edge configured to engage tissue and inhibit rotational movement and inhibit axial movement of the proximal head in a distal direction, the proximal head being sized to fit within an intramedullary canal of a more-proximal phalanx portion of said one of a finger and a toe; and 
 a rigid body extending between and connecting the distal head and the proximal head, the body having a rigidity sufficient to withstand bending loading applied by the phalanges, the rigid body comprising a main portion, a distal neck portion connecting the rigid body to the distal head, and a proximal neck portion connecting the rigid body to the proximal head, the distal and proximal neck portions having a cross-sectional area smaller than a cross-section area of the main portion such that tissue ingrowth may occur behind the distal head around the distal neck portion and behind the proximal head around the proximal neck portion; and 
 
 insertion forceps configured to securably grasp the intramedullary fixation device, the insertion forceps comprising:
 a first nose piece having a first recess formed therein, the first recess being sized to receive a portion of the body of the intramedullary fixation device; 
 a second nose piece having a second recess formed therein, the second recess being sized to receive a portion of the body of the intramedullary fixation device, the first and second nose pieces being cooperatively arranged to securely grip the body of the intramedullary fixation device sufficiently to prevent rotation and axial displacement under normal insertion conditions. 
 
 
     
     
       13. The kit of  claim 12 , further comprising:
 a reamer sized for insertion into an intramedullary canal of a human toe, the reamer having a first diameter; and 
 a broach having a second diameter larger than the first diameter. 
 
     
     
       14. An intramedullary fixation device used in bone fixation and stabilization, comprising:
 an arrowhead-shaped distal head comprising a distal end, the distal head having first, second, third, and fourth outwardly facing side surfaces forming a pyramidal shape, the first and third side surfaces being opposed from each other and forming a first angle, and the second and fourth side surfaces being opposed from each other and forming a second angle, the second angle being different than the first angle, the first, second, third, and fourth side surfaces converging toward the distal end, each of the first and third side surfaces having a proximally projecting edge configured to engage tissue and inhibit rotational movement and inhibit axial movement of the distal head in a proximal direction, the distal head being sized to fit within an intramedullary canal of a more-distal phalanx portion of one of a finger and a toe; 
 an arrowhead-shaped proximal head comprising a proximal end, the proximal head having fifth, sixth, seventh, and eighth outwardly facing side surfaces, the fifth and seventh side surfaces being opposed from each other and forming a third angle, and the sixth and eighth side surfaces being opposed from each other and forming a fourth angle, the third angle being different than the fourth angle, the fifth, sixth, seventh, and eighth side surfaces converging and meeting at the proximal end, each of the fifth and seventh side surfaces having a distally projecting edge configured to engage tissue and inhibit rotational movement and inhibit axial movement of the proximal head in a distal direction, the proximal head being sized to fit within an intramedullary canal of a more-proximal phalanx portion of said one of a finger and a toe; and 
 a rigid body extending between and connecting the distal head and the proximal head, the body having a rigidity sufficient to withstand bending loading applied by the phalanges, the rigid body being sized and shaped to fit within the intramedullary canals of both the more-distal phalanx portion and the more-proximal phalanx portion, the distal head, proximal head, and rigid body being sized and shaped so that the more-distal phalanx portion may abut directly against the more-proximal phalanx portion when the distal head is in the more-distal phalanx portion and the proximal head is in the more-proximal phalanx portion. 
 
     
     
       15. The intramedullary fixation device of  claim 14 , the rigid body comprising a main portion, a distal neck portion connecting the rigid body to the distal head, and a proximal neck portion connecting the rigid body to the proximal head, the distal and proximal neck portions having a cross-sectional area smaller than a cross-section area of the main portion such that tissue ingrowth may occur behind the distal head around the distal neck portion and behind the proximal head around the proximal neck portion. 
     
     
       16. The intramedullary fixation device of  claim 14 , wherein the side surfaces are smooth, planar surfaces. 
     
     
       17. The intramedullary fixation device of  claim 14 , wherein the first angle is larger than the second angle and the third angle is larger than the fourth angle. 
     
     
       18. The intramedullary fixation device of  claim 14 , wherein the first angle is larger than the third angle. 
     
     
       19. The intramedullary fixation device of  claim 14 , wherein the second and fourth side surfaces include proximal ends that relatively smoothly transition to the body. 
     
     
       20. The intramedullary fixation device of  claim 14 , wherein the second and fourth surfaces intersect with a surface of the distal neck portion, and wherein the first and third surfaces do not intersect with a surface of the distal neck portion.